Inflammatory bowel disease, wherein Crohn's disease and ulcerative colitis are its main typical diseases, is an intractable disease which occurs at a relatively young generation and causes symptoms such as abdominal pain, fever, diarrhea and melena. Crohn's disease is a idiopathic granulomatous inflammatory disorder in which lesion progresses from ulcer, fibrosis and then to stricture, in discontinuously from mucosa to whole layers of intestinal tract through all digestive tracts from mouth to anus, and is defined as a disorder that shows systemic symptoms such as abdominal pain, chronic diarrhea, fever and malnutrition. Also, ulcerative colitis is an idiopathic diffuse non-specific inflammation of the large intestine, which mainly affects mucosa and frequently forms erosion and ulcer and is a disease which shows various general symptoms including bloody diarrhea. Other inflammatory bowel diseases, namely enteritis occurring in small intestine or large intestine, include intestinal Behcet's disease, hemorrhagic rectal ulcer, pouchitis and the like. Regarding the cause of inflammatory bowel disease, it is considered that an abnormal immune function is concerned, but its exact cause is not known yet (Non-patent Reference 1 and 2).
Immunosuppressants, steroids, salazosulfa-pyridine, mesalazine and the like are used in the medication of inflammatory bowel disease. Regarding the immunosuppressants, it is said that antimetabolites, particularly azathiopurine, 6-mercaptopurine and the like, are effective for Crohn's disease, but these are low in the clinical effect at early stage of administration and frequently show side effects such as allergy, pancreatitis and leukopenia. Ciclosporin at a high dose shows therapeutic effect for inflammatory and fistula diseases, but its long-term use is contraindication because of various toxicities. A monoclonal antibody or infliximab which inhibits tumor necrosis factor is used by intravenous injection for moderate or severe Crohn's disease (particularly accompanied by fistulas) having resistance to other treatments, but its long-term effects and side effects have not been revealed. As the other convincing immune regulation therapy, an interleukin-1 inhibitor, an antibody for interleukin-12, an anti-CD4 antibody, an adherent molecule inhibitor, a down regulatory cytokine or a monoclonal antibody for tumor necrosis factor have been tried. Though there are many such experiential therapeutic approaches, the current drug therapy for inflammatory bowel disease is imperfect. Accordingly, it has been hoped the development of a medicine which is further effective with high safety (Non-patent References 3, 4 and 5).    Non-patent Reference 1: Research and Study Group on Specific Disease Intractable Inflammatory Intestinal Disease, Ministry of Welfare, Research Report in 1997    Non-patent Reference 2: New Engl. J. Med., 2002, 347: 417-429    Non-patent Reference 3: Am. J. Gastroenterol., 2001, 96: 1977-1997    Non-patent Reference 4: Nucl. Med. Commun., 2005, 26: 649-655    Non-patent Reference 5: Saishin Igaku (Newest Medical Science), 2004, 59: 1070-1075